Good point. I liked Laura but yes, she did come across as weak in places especially in the area that Kylie pointed out above in a spoiler hidden comment where her reaction doesn't really make sense. I think Carmilla is a more flawed novel than Dracula. As has been pointed out already it leaves many unanswered questions. Dracula is a much tighter work.
I have to disagree here. I did find Mina, and many of the characters in Dracula, 'too good to be true'. I had to suspend belief a little in order to take on their good and noble hearts. However it did not spoil the book for me and I actually enjoyed those qualities in the characters, even though I know I will never meet people like that in real life . The characters still worked.